1. Field of the Invention
The present invention relates to a bonded structure of a touch screen, and more particularly, to a bonded structure of a touch screen with a flexible circuit board for preventing overflow and a bonding method thereof.
2. Description of the Prior Art
For convenience in operation, people recently replace the mouse or the keyboard with the touch screen. The users should use a finger or other objects to touch screen assembled in front of the display, and then, the system could locate the selected input information according to the pattern or the function list touched by the finger. The touch screen is composed of a touch detecting device, such as touch sensor, and a touch screen controller. The touch sensor is assembled in front of a liquid crystal display screen and used to detect a position touched by user. The touch sensor is connected to a printed circuit board of the touch screen controller through a flexible circuit board. The main function of the touch screen controller is to receive touch information from the touch sensor, and to convert it into touch point coordinate. Further, the touch point coordinate is sent to the CPU, and the touch screen could receive the command from CPU and execute it simultaneously.
In order to achieve a design of a capacitive touch sensing, the transparent touch sensor must be sandwiched between transparent protective layers regularly. The transparent touch sensor usually is transparent conductive film, which is indium tin oxide (ITO) film. The ITO has good conductivity and transparency.
Any void generated by uneven bonding would reduce touch function and affect appearance of product. In order to guarantee better bonding, the UV adhesive should be used due to having the advantages of convenient usage, thin adhesive layer, and high optical quality (transparency larger than 95%).
However, as shown in FIG. 1, after an end of a flexible circuit board 6 for connecting the touch screen controller is bonded on the touch sensor panel 1, the bonding area of the flexible circuit board 6 has a height. Furthermore, before bonding the touch sensor panel 1 to a transparent protective layer, the UV adhesive should be uniformly coated on the touch sensor panel 1, and the height of the bonding area of the flexible circuit board 6 would have capillary action to drain the liquid UV adhesive, and the UV adhesive would be overflowed from the bonding area of the flexible circuit board 6 due to the height of the flexible circuit board 6. Thus, the flexible circuit board 6 at the bonding area has much overflowed adhesive 3, and the spilled adhesive 3 even has a depth of 5 to 7 millimeter or more, which directly affect the following assembling process and doesn't conform the manufacturing requirement.